Hudson. — Oji Seasonal Time. 579 



air and sunshine ; and the probable resultant increase in the 

 health, morality, and happiness of the community generally. 



" The foregoing remarks are framed to apply to us in the 

 Southern Hemisphere, but with the seasons reversed they 

 would, of course, apply with equal force to the Northern 

 Hemisphere." 



It cannot be too strongly borne in mind that the time 

 standard in ordinary use — i.e., the mean solar day — is merely 

 an abstraction devised for human convenience, and does not 

 represent any actual time interval existing in nature. The 

 shortest actual and unchangeable time-unit is the sidereal day, 

 or the interval of time taken by the earth in performing one 

 complete rotation on its axis, a measurement which is wholly 

 unsuited to human requirements. The length of the sidereal 

 day is 23 hours 56 minutes 4-091 seconds, the sidereal time, 

 as shown by an observatory clock, thus gaining approxi- 

 mately four minutes each day on the ordinary clock keeping 

 mean solar time. As the sun is not a fixed point in the 

 sky, but is apparently continually moving towards the east, 

 owing to the revolution of the earth around the sun, the earth 

 requires to make a little more than one rotation on its axis 

 to bring the sun to the same position each day. This 

 apparent easterly movement of the sun is the cause of the 

 four minutes difference between the sidereal and the solar 

 day. 



Owing to the sun's apparent movement in the sky not 

 being absolutely uniform, but being quickest in December, 

 when we are nearest to the sun, and slowest in June, when 

 we are furthest from him, it is necessary to add or subtract a 

 variable amount in order to obtain a uniform average length 

 of twenty-four hours for each day. This amount, which is 

 added to, or subtracted from, the apparent time as given by 

 the sun, is called the "equation of time," and is stated in 

 most almanacs against each day in the year to which it refers. 

 The equation of time is greatest early in November, when the 

 apparent time as shown by the sun is no less than sixteen 

 minutes in advance of mean time. In Wellington there is, in 

 addition, a constant difference of nine minutes between local 

 time and the New Zealand mean time which is employed 

 throughout the colony; so that, in the early part of November, 

 our clocks indicate a time no less than twenty-five minutes 

 behind that shown by the sun — in other words, when the sun 

 is on the meridian on the 3rd November the time according 

 to our clocks is only 11.35 a.m. 



I have been careful to specially point out these various 

 adjustments, which are used by astronomers in computing the 

 standard time, in order to show that the time in ordinary use 

 is only an abstraction, so to speak, specially arranged to suit 



